Process for control of microbial contamination, mineral suspensions obtained and their uses

ABSTRACT

The invention concerns a process for disinfection and/or conservation and/or reduction and/or control of microbial contamination of aqueous dispersions and/or aqueous suspensions of mineral matter, providing satisfactory stability in terms of Brookfield™ viscosity for the said aqueous dispersions and/or suspensions of mineral matter. It also concerns the said aqueous dispersions and/or suspensions thus obtained, together with their uses in the mineral, paper and paint industries. Finally it concerns the end products obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is continuation of U.S. application Ser. No. 11/794,511, filed Jun.27, 2007, which is a U.S. national phase of PCT Application No.PCT/IB2006/000151, filed Jan. 20, 2006, which claims priority to FrenchApplication No. FR0500779, filed Jan. 26, 2005, the contents of which ishereby incorporated by reference.

The invention concerns in the first instance a process for disinfectionand/or conservation and/or reduction and/or control of microbialcontamination of aqueous dispersions and/or aqueous suspensions ofmineral matter, providing satisfactory stability in terms of Brookfield™viscosity for the said aqueous dispersions and/or suspensions of mineralmatter.

Another purpose of the invention lies in aqueous suspensions and/ordispersions of mineral matter, having satisfactory stability in terms ofBrookfield™ viscosity and having a very small number of microbial germsand/or of which the concentration of microbial germs can be controlledby means of the process according to the invention,

Another purpose of the invention consists in the use of the said aqueoussuspensions and/or dispersions of mineral matter in the mineralindustry, in the paper industry, preferably in the manufacture of paper,and/or in paper coating, and also in the field of manufacture ofwater-based paints, and notably lacquers and varnishes.

A final purpose of the invention lies in mineral formulations, paperformulations and notably paper sheets and coating colours, water-basedpaints, lacquers and varnishes characterised in that they contain thesaid aqueous suspensions and/or dispersions of mineral matter accordingto the invention.

A first object of the invention is thus a process for disinfectionand/or conservation and/or reduction and/or control of microbialcontamination of suspensions and/or of aqueous dispersions of mineralsand/or of fillers and/or of pigments, for protection faced withmicrobial contamination and/or deliberate control of the growth of amicroorganism during the preparation of the said dispersions and/orsuspensions, of their storage, of their transport, and at the time oftheir modification and/or treatment over an interval of time which maybe determined by the user. The process is preferably used in mines, inthe paper industry and in the varnishes and paints industry.

The aim of the process is essentially to reduce the concentration ofand/or to avoid traditional biocides as, notably, specified in “XXXVIEmpfehlung” vom BgVV (Bundesinstitut für gesundheitlichenVerbraucherschutz und Vetrinärmedizin, Deutschland) in “Kunststoffe imLebensmittelverkehr” Carl Heymanns Verlag kg, Köln, Berlin, Bonn, Munichand in Federal Code 21 §176.300, revision of 1 Apr. 2001. As aconsequence it reduces the risks of contamination and poisoning forhumans, and of damage to the environment when such biocides were usedaccording to the prior art, alone, and in generally high concentrations.

Another aim is to create a process incorporating a time interval, whichmay be chosen freely, during which the system must act.

Another major aim is not to influence, or, if this were to beunavoidable, to influence in a positive manner, the properties of theprocessed products and/or their subsequent use.

Another aim is to combine such a treatment in the habitual stages ofmanufacture of minerals and/or pigments and/or fillers such as, notably,the common stages of dispersion and/or grinding in water of the saidfillers.

A final aim is to provide a process which does not modify the long-termstability of the Brookfield™ viscosity of the aqueous suspensions anddispersions of mineral matter thus obtained.

In the present application, the following is designated through the term“microbes”: every organism and/or microorganism, aerobic or anaerobic,of a bacterial nature, such as bacterial germs, and notably mesophilicaerobic bacterial germs, such as pseudomonas aeruginosa, salmonellaenteritidis and escherichia coli, as gram-negative representatives, andbacillus subtilis, staphylococcus aureus, listeria monocytogenes andmicrococcus luteus, as gram-positive representatives, but also anaerobicbacterial germs and anaerobic sulphate reducing bacterial germs, such asdesulfovibrio desuifaricans, but also fungi, and notably aspergillusniger, together with yeasts, and notably saccharomyces cerevisiae.

Through the expression “disinfection and/or preservation” it is alsounderstood that water and/or aqueous solutions and/or aqueoussuspensions and/or aqueous dispersions containing mineral matter areprotected against a microbial attack and/or are protected against a riskof microbial infection, principally by prevention of growth and/or bydestruction of the said microbes.

These notions of disinfection and of preservation thus cover all thecurative and protective effects in terms of protection of the saidaqueous suspensions and/or dispersions of mineral matter in relation toa microbial attack.

Finally, the terms “dispersions” and “suspensions” of mineral matterrefer in the present application to a composition containing water,mineral matter the concentration by dry weight of which is greater thanor equal to 0.1% relative to the total weight of the said dispersionsand suspensions, and possibly other additives such as notably dispersingagents, grinding aid agents and anti-foaming agents.

Currently, to accomplish disinfection and protection of water and/oraqueous solutions and/or aqueous suspensions and/or aqueous dispersionscontaining mineral matter, the skilled man in the art has two types ofsolutions, which he may use alone or in combination: the use of organicchemicals referred to under the term biocides, or the use of treatmentprocesses not involving these biocides. The Applicant will now presentthe state of the technique relative to both these approaches, whilsthighlighting the disadvantages constituted by all these currentsolutions.

Aqueous dispersions and suspensions of minerals and/or fillers and/orpigments are habitually conserved using biocides which can be appliedindividually or in combination. Habitual substances with a biocidaleffect for use in aqueous suspensions and/or aqueous dispersions ofmineral matter and in industrial circuit water are, notably, listed inthe Code of Federal Regulations 21, §170 to §199, modified in April2000, section 176.300, Slimicides. Such substances are also covered inthe work “Praxis der Sterilisation, Desinfektion-Konservierung” by KarlHeinz Wallhausser, completely revised 5^(th) edition published by GeorgThieme Verlag, Stuttgart and in the document “Microbicides for theprotection of materials, a handbook by Wilfried Paulus” first edition1993, published by Chapman & Hall, 2-6 Boundary Row, London SE1 8HN. Inaddition in the “Code of Federal Regulation 21, §170 to §199, modifiedin April 2001, such substances with biocidal effects are described insections 176.170 and 176.300”.

Among the widely used biocidal formulations, some contain 1.2benzisothiazoline-3-on. The disadvantage of such formulations it is whatis called a “pseudomonas window”, i.e. the substance has a biocidaleffect against many bacteria but nevertheless has a lesser effectivenessagainst certain bacteria, in this instance the pseudomonas. Moreover,this substance causes cutaneous sensitisation and is consequentlydangerous for the users. Another disadvantage lies in the stability ofthe said product, such that during a subsequent application thebactericidal effect of 1.2 benzisothiazoline-3-on is not cancelled andit can then influence food products by traversing packaging substancesfor such products and/or utility objects for food products. In addition,the poor degradability of this compound and its strong toxicity have adestructive effect on the environment in the event that the said productmigrates through the packaging containing it, or in the event ofdegradation of the said packaging.

Moreover, the skilled man in the art can also use mixtures of5-chloro-2-methyl-4-isothiazolinon and 2-methyl-4-isothiazolinon. Here,the disadvantage lies in the fact that only5-chloro-2-methyl-4-isothiazolinon manifests a sufficient efficacyrelative to bacteria; and this substance is very unstable when exposedto alkaline pH values and to heat, and consequently rapidly loses itseffectiveness when it is used in alkaline pH conditions and/or attemperatures higher than 40° C. In addition, these substances also havea sensitising effect on skin.

It is also possible to use substances containing bromine and, moregenerally, combinations of halogenated products. Such combinations arehowever undesirable in many cases since they can damage the environment,particularly in the field of danger of exposure to water. Due to theirinstability for a neutral and alkaline pH value, such biocides must inall cases be stabilised at an acid pH value and are used as such. In thecase of a dosage made once and/or several times, problems ofcompatibility can occur with pigment solutions adjusted to a neutraland/or alkaline pH. The stability of such solutions can consequently bedegraded in terms of their Brookfield™ viscosity. Very particularly foraqueous dispersions or suspensions with high concentrations of mineralmatter, notably calcium carbonate and/or kaolin, it is possible toobserve an increase of the viscosity and formation of agglomerates.

It is also known to use glutardialdehyde. Glutardialdehyde is unstableabove temperatures of 40 to 45° C. and decomposes or forms ring-likestructures, thus losing its efficacy. In addition, glutardialdehyde iscurrently the subject of many toxicological studies, relating notably toits carcinogenic character: it is, indeed, not certain that this productis devoid of all risks for humans in mutagenic terms. Although thisaspect is not yet clearly demonstrated, conversely it is well known thatglutardialdehyde can cause chronic respiratory illnesses and allergiccomplaints. Consequently, it represents a definite danger fix the users.

Another very large group of biocides lies in products which decomposegiving formaldehyde. Generally speaking, these products are not verystable under heat and decompose spontaneously into formaldehyde attemperatures over 60° C. Formaldehyde is moreover suspected to becarcinogenic: according to a classification established by the EuropeanUnion, it is placed in category no°3 as a “substance preoccupying forhumans due to possible carcinogenic effects” and, due to its highvolatility (T_(eb)=−19.2° C. for the pure product), it represents amajor risk in the event of use. O-formals and N-formals, ethylene glycolbis hemiformal and benzyl-bis-hemiformal are mainly used as formaldehydedissociators. According to the work entitled “Praxis der Sterilisation,Desinfektion-Konservierung, by Karl-Heinz Wallhausser, completelyrevised 5^(th) edition, published by Georg Thieme Verlag, Stuttgart,1995, page 43”, it is known that phenol derivates are used asanti-microbial active principles.

In document DE 100 27 588 A1, o-phenylphenol and its alkaline salts areproposed as preservation agents. The latter are indeed stable for analkaline pH and active against most microorganisms but, due to theirsatisfactory chemical and thermal stability, it is however difficult todeactivate them. It is sometimes essential that their anti-bacterialeffect should not be permanent: this is a requirement of the highestimportance which is found notably in the paper manufacturing field.Thus, document WO 04/901.48 describes the enzymatic synthesis of apolymer of the acrylamide type, used as a coagulant and/or adhesiveand/or thickening agent in the manufacture of paper. Furthermore,document CN 1 483 773 teaches the use of an enzymatic compound in aprocess to deink paper. One may also mention document JP 2004 169 243,which describes a process using an enzyme to whiten pulp used in themanufacture of paper. Consequently, these documents satisfactorilydemonstrate the importance which certain enzymes may have in the papermanufacturing field: it is thus important to have a microbial protectionmeasure the activity of which it is possible to control, in order not toharm the presence of the said enzymes, which are essential in certainpaper manufacturing processes. In addition, it is known thato-phenylphenol has both a curative and a protective effect: both ofthese aspects are of equal importance for the skilled man in the art. Acurative and protective effect is taken to mean respectively thecharacters of a process or a substance intended to ensure protectionrespectively against a subsequent infection or against an infectionwhich has already occurred (as described in the document “Wörterbuch derMikrobioiogie H. Weber, Gustav Fischer Verlag, Jena, Stuttgart, Lüber,Ulm”, 1997, respectively on page 449 and page 321).

In addition, processes of dosing of microbial substances fordisinfection and preservation of aqueous suspensions and/or dispersionshave disadvantages in the areas of human protection, stability underheat and/or damage to the environment: their use must thus be avoided.

Another method to ensure the disinfection and preservation of waterand/or of aqueous suspensions and/or of aqueous dispersions containingmineral matter lies in the use of treatment processes which do notinvolve chemicals.

In this respect, in the field of food products, firstly, substances witha microbicidal effect are sterilised and preserved, using notably heat(for example UHT process). Too high a heat can, however, lead to amodification of the products to be protected and cannot consequently berecommended in many cases. Vitamins, for example, can be destroyed bytoo high a temperature.

In the literature processes making use of electrophoresis are alsodescribed. In this case, hydrogen or oxygen in the nascent state isgenerated. However, it is well known that hydrogen in the nascent state,particularly in the presence of oxygen, poses a risk of explosion(explosive gas).

It is also known to accomplish sterilisation by means of X rays. Sourcesof X rays can however be dangerous if they are handled in anon-compliant manner; they require specially trained personnel andconsequently have the disadvantage of being costly and difficult to putto use.

Furthermore, it is known that ozone is used as a disinfection agent.Ozone is however toxic and costly to manufacture and is consequently notespecially suitable for use on site. Ozone can also degrade the effectof dispersing agents such as sodium polyacrylates which, again, leads toan undesirable increase of the viscosity of the aqueous suspensionand/or dispersion to be treated.

UV radiation is also used, particularly UV-C radiation forsterilisation. UV radiation is however dangerous. UV light, for example,is used in sterilisation of water. Cloudy substances can however bepoorly treated by the use of UV radiation (shadow phenomena).

“Hochschule CH-8820 Wädenswil”, Switzerland, publishes a process whichreduces bacteria by using strong electrical impulses (“High ElectricField Puls” process and ASE/AES bulletin 3/01, page 44): this alsoconcerns a process which requires major modifications to the mineralmatter manufacturing process for it to be used.

In addition, in the work “J. Food Prot. Vol. 64 No. 10 2001, pages 1579to 1583, Author-Department of Applied Chemistry, Kanagawa Institute ofTechnology, Atsugi, Japan”, a process for the disinfection of foodproducts is described using charred crab shells. In this process shellsare cooked at a temperature of over 850° C. and the CaO produced isproposed as a disinfectant agent for food products. The details of anynegative effects on the processed products are not gone into. Theskilled man in the art cannot, on the basis of this document, obtain anyknowledge whatever concerning the influence produced on aqueoussuspensions or dispersions of pigments obtained and on the modificationof their properties, such as viscosity properties. In addition, nothingis said on the subject of an efficacy limited over time, and noreference is given to another possible treatment aimed at creating atime interval during which the system must act.

In addition, in Brock-Biology of Microorganisms—(9^(th) edition),Madigan, M. T., and Martinko, J. M., and Perker, J., 2000, Upper SaddleRiver, (Prentice-Hall, Inc.), pages 154 to 155 in FIG. 5.18 and in“Allgemeine Mikrobiologie, (7^(th) edition), Schlegel, H. G., 1992,Georg Thieme Verlag, Stuttgart—New York, pages 194 to 196, it ismentioned that several microorganisms such as bacillus species can alsolive in an extremely alkaline environment. In this document, no mentionis made of the fact that, by increasing or reducing the pH value, it ispossible to obtain a temporary preservation of the aqueous suspensionsof mineral matter without modifying the physical properties of the saidsuspensions in terms of viscosity. Moreover, this document, which wouldtend to demonstrate that certain microorganisms can subsist in alkalinepH conditions, does not encourage the skilled man in the art to put suchalkaline pH conditions to use, precisely with a view to protectingand/or disinfecting aqueous suspensions of mineral matter, which is anobject of the present invention. The Applicant is keen to stress thatneither this process, nor the methods using heat, ozone, X or UV rays orelectrical impulses, allow microbial growth to be controlled in themineral matter suspensions to be treated. As it has been previouslystated, this is an important requirement for the skilled man in the art,notably in the paper manufacturing industry.

Finally, document DE 19 811 742 describes a water treatment process topurify it with calcium carbonate and kaolin, by increasing the pH to avalue of over 12, and preferentially over 12.6-12.8, through theaddition of calcium oxide or hydroxide. This document, which isundoubtedly not in the special technical field of processes fortreatment of aqueous suspensions of mineral matter to eliminate bacteriafrom them, cannot be passed over by the skilled man in the art: itrefers to a more general process for treatment of such mineral mattersuspensions, with a view to purifying them. It teaches that the additionof calcium oxide or hydroxide leads in this case to a flocculation ofthe suspended mineral matter, which is an unsought effect in connectionwith the technical problem which the Applicant is seeking to resolve(reduction or control of microbial growth). However, in a surprisingmanner, using the process developed in the present application, theproblem posed is successfully resolved without however causing thesuspended mineral matter to become flocculated, possibly through theaddition of calcium oxide or hydroxide. Thus, in a surprising manner,the process according to the invention does not lead to a flocculationof the aqueous suspensions and dispersions of mineral matter to which itis applied.

Ultimately, use of biocides such as described in the prior art has manydisadvantages, in terms of danger for humans and/or damage to theenvironment.

Secondly, the processes currently used to decontaminate aqueoussuspensions of mineral matter generally prove costly, difficult toincorporate in a process to manufacture the said mineral matter, andalso, hr their part, not free of dangers for the environment and risksfor humans.

Furthermore, none of the habitual chemicals and none of the knownprocesses of decontamination allow control of the development of growth,i.e. development of the cell division of the microbes and/or the totalnumber of microbes over time, in the said aqueous suspensions of mineralmatter. But, as the Applicant has previously indicated, this is afundamental requirement for the skilled man in the art, notably in thepaper manufacturing sector.

In addition, it is primordial to develop a process which does not modifythe stability, in terms of the Brookfield™ viscosity, of the aqueousdispersions and/or suspensions of mineral matter thus obtained.

These problems are entirely resolved by the invention which consists ina process for disinfection and/or preservation and/or reduction and/orcontrol of microbial contamination of aqueous dispersions and/orsuspensions of mineral matter, characterised in that it uses:

-   -   a) at least one stage to increase the OH⁻ ion concentration of        the said aqueous dispersions and/or suspensions, to a value        greater than or equal to 1×10⁻² mole/l,    -   b) at least one stage of dispersion and/or grinding of the said        aqueous dispersions and/or suspensions, occurring before, during        or after stage a), possibly using at least one dispersing agent        and/or at least one grinding aid agent,    -   c) possibly at least one stage to reduce the OH⁻ ion        concentration of the said aqueous dispersions and/or        suspensions, occurring after stage a), to a value less than or        equal to 1×10⁻² mole/l,    -   d) possibly at least one stage of addition of at least one        substance with a microbicidal effect and/or use of a physical        decontamination process occurring before, during or after        stage a) and/or b) and/or c).

The Applicant stresses that, once the process has thus been defined,stages a), b), c) and d) can be repeated as many times as required, asthe skilled man in the art shall see fit; the latter shall know how toadapt the process according to the invention to the aqueous dispersionsand/or suspensions of mineral matter which he envisages treating.

This process is thus characterised by an increase of the OH⁻ ionconcentration using one or more OH⁻ ion donators, such as alkalineand/or alkaline earth oxides and/or alkaline and/or alkaline earthhydroxides, to reduce the speed of the biological cell division and/orcause the biological cell division to cease and/or to destroy themicrobes present in the said aqueous dispersion and/or suspension.

And, as required, the OH⁻ ion concentration of the aqueous suspensionand/or dispersion is reduced, using one or more weak, moderately strongor strong, monovalent and/or polyvalent H₃O+ ion donators, such as,notably, gaseous CO₂ dissociated in carbonic acid water; this enablesthe natural growth of the microbial germs to be re-established.

This process allows, both in the phase to limit the growth of microbialgerms, and in the phase of propagation of the said germs, alldeterioration of the aqueous suspension and/or dispersion of mineralmatter to be prevented with regard to its subsequent application, suchas, for example, a deterioration of its suitability for storage, of itspumpability, and/or any modification of its rheological properties interms of viscosity.

An important aim of the invention is thus to simplify the procedure ofdisinfection and/or preservation of the aqueous suspensions and/ordispersions of mineral matter in combination with other manufacturingstages, such as, notably, grinding and/or dispersion of the said mineralmatter, without however modifying the stability in terms of theBrookfield™ viscosity of the said aqueous suspensions and/or dispersionsof mineral matter.

Another aim of the invention is to provide an aqueous suspension and/ordispersion of mineral matter by a process allowing disinfection and/orprotection of the said suspension and/or the said aqueous dispersionagainst all microbial contamination and/or microbial attacks, whilstdoing minimal damage to humans, the environment or natural resources. Inparticular it is necessary to ensure that risky chemical substances arenot used unnecessarily, bearing in mind that the combination of theprocess according to the invention, with the appropriate quantitiesused, of minimal harmfulness and/or lower quantities, of chemicalsubstances, such as, for example, o-phenylphenol and its salts, mayconstitute a preferred embodiment. The process must be able to beapplicable to aerobic and anaerobic species.

Another important aim of the invention is to control the development ofgrowth, i.e. development of biological cell division and/or the totalnumber of microorganisms over time, so as not to exceed a determinednumber of microbes. In addition, the microbicidal effect may besuppressed in a simple manner, without modifying the stability of theaqueous suspensions and/or dispersions treated in terms of Brookfield™viscosity, without restricting their subsequent uses, notably in thepaper manufacturing sector, through the use of enzymes, which isperfectly compatible with the process according to the invention.

Another aim of this invention concerns the purification and thedisinfection of storage tanks, rail and road transport recipients, suchas concrete and steel tanks, rail tanker wagons, tanks and containers.Rail tanker wagons which are used for transporting aqueous suspensionsof pigments contain residual quantities of pigments in liquid form,which are partly concentrated by drying. On their return, they must becleaned and disinfected to prevent all contamination of a new product tobe loaded. The same applies for every storage and transport “recipient”,whatever its size and volume. In this case, too, it is essential tocancel the “just in time” microbicidal effect in order not to exposehumans, animals and the environment to any danger.

The problem is resolved according to the invention due to the fact thata process is provided which, alone or in combination with otherprocesses, such as the additional use of appropriate substances with amicrobicidal effect or a physical process, such as high voltage pulses,or thermal treatment, allows reduction and/or elimination and/or controlof the growth of the microbial organisms, a process which has a limitedaction time and can be controlled. The process thus has as many curativeeffects as it has protective ones. Finally, the said process does notmodify, or modifies only slightly, the stability, in terms ofBrookfield™ viscosity of the said aqueous dispersions and/or suspensionsof mineral matter thus treated.

The first object of the invention is thus a process for disinfectionand/or preservation and/or reduction and/or control of microbialcontamination of aqueous dispersions and/or suspensions of mineralmatter, characterised in that it uses:

-   -   a) at least one stage to increase the OH⁻ ion concentration of        the said aqueous dispersions and/or the said aqueous        suspensions, to a value greater than or equal to 1×10⁻² mole/l,    -   b) at least one stage of dispersion and/or grinding of the said        aqueous dispersions and/or suspensions, occurring before, during        or after stage a), possibly using at least one dispersing agent        and/or at least one grinding aid agent,    -   c) possibly at least one stage to reduce the OH⁻ ion        concentration of the said aqueous dispersions and/or        suspensions, occurring after stage a), to a value less than or        equal to 1×10⁻² mole/l,    -   d) possibly at least one stage of addition of at least one        substance with a microbicidal effect and/or use of a physical        decontamination process occurring before, during or after stage        a), and/or b), and/or c).

This process is characterised in that the OH⁻ ion concentration valuerelative to stage a) is preferentially higher than or equal to 2×10⁻²mole/l.

This process is also characterised in that the OH⁻ ion concentrationincrease, relative to stage a), is undertaken using one or more OH⁻ iondonators, such as alkaline and/or alkaline earth oxides and/or alkalineand/or alkaline earth hydroxides.

This process is also characterised in that the OH⁻ ion concentrationvalue relative to stage c) is preferentially less than or equal to1×10⁻³ mole/l, and very preferentially less than or equal to 1×10⁻⁴mole/l.

This process is also characterised in that the OH⁻ ion concentrationreduction, relative to the possible stage c), is undertaken using one ormore weak, moderately strong or strong, monovalent and/or polyvalentH₃O⁺ ion donators, such as notably gaseous CO₂ dissociated in carbonicacid water.

This process is also characterised in that the possible stage d) ofaddition of at least one substance with a microbicidal effect and/or useof a physical process of microbicidal decontamination uses at least onebiocide and notably o-phenylphenol and/or its salts or indeed theirmixtures, and/or at least one product containing a germ which destroysmicrobial germs, preferably pseudomonas germs, and more preferablypseudomonas aeruginosa germs, and in that the destructive germ is of theBdellovibrio family, and is very preferentially the Bdellovibriobacteriovorus germ.

This process is also characterised in that the possible stage d) ofaddition of at least one substance with a microbicidal effect and/or useof a physical process of microbicidal decontamination uses at least onephysical process, such as preferentially processes based on an increaseof temperature.

In an embodiment of this process corresponding to the accomplishment ofstage c), the said process is characterised in that stage c) occurspreferentially between one week and one month after stage a).

According to this embodiment, no substance with a microbicidal effect isthen used in the aqueous dispersions and/or suspensions of mineralmatter to be treated.

This process is also characterised in that it may be useddiscontinuously, semi-continuously or continuously, according to theterminology with which the skilled man in the art is very familiar.

This process is also characterised in that it has curative and/orprotective effects with regard to the waters and/or aqueous dispersionsand/or suspensions of mineral matter to be treated.

This process is also characterised in that the minerals and/or pigmentsand/or fillers which it uses are chosen from among kaolin, aluminiumhydroxide, titanium dioxide, talc, gypsum, satin white, mica, mineralsand/or fillers and/or pigments containing calcium carbonate, and inparticular natural calcium carbonates, marble, limestone, dolomite ortheir mixtures, their mixtures with other minerals, such as talc-calciumcarbonate mixtures, calcium carbonate-kaolin mixtures, or again mixturesof calcium carbonate with aluminium trihydroxide or aluminium trioxide,or again mixtures with synthetic or natural fibres, or againco-structures of minerals such as talc-calcium carbonate ortalc-titanium dioxide co-structures, or their mixtures, and/or calciumcarbonates containing dolomite, together with calcium carbonatesmanufactured in a synthetic manner by precipitation and/or calciumcarbonate precipitates with other minerals. Preferentially, theseminerals and/or pigments and/or fillers are chosen from among naturaland/or precipitated calcium carbonate, and very preferentially arechosen from among natural calcium carbonates and notably from amongmarble, calcite, chalk and their mixtures.

Finally, this process is characterised in that it is used in mineralindustry fields, and notably in storage tanks, rail and road transportrecipients, such as concrete and steel tanks, rail tanker wagons, tanksand containers, in the paper industry, preferably in papermanufacturing, and/or in coating colours, and in the field of themanufacture of water-based paints and also in lacquers and varnishes.

Another object of the invention lies in aqueous dispersions and/orsuspensions of mineral matter obtained by use of the process accordingto the invention.

These dispersions and/or suspensions are also characterised in that theycontain a mineral and/or pigment and/or filler chosen from among kaolin,aluminium hydroxide, titanium dioxide, talc, gypsum, satin white, mica,minerals and/or fillers and/or pigments containing calcium carbonate,and in particular natural calcium carbonates, marble, limestone,dolomite or their mixtures, their mixtures with other minerals, such astalc-calcium carbonate mixtures, calcium carbonate-kaolin mixtures, oragain mixtures of calcium carbonate with aluminium trihydroxide oraluminium trioxide, or again mixtures with synthetic or natural fibres,or again co-structures of minerals such as talc-calcium carbonate ortalc-titanium dioxide co-structures, or their mixtures, and/or calciumcarbonates containing dolomite, together with calcium carbonatesmanufactured in a synthetic manner by precipitation and/or calciumcarbonate precipitates with other minerals. Preferentially, theseminerals and/or pigments and/or fillers are chosen from among naturaland/or precipitated calcium carbonate, and very preferentially arechosen from among natural calcium carbonates and notably from amongmarble, calcite, chalk and their mixtures.

In a first embodiment in which stage c) of the process according to theinvention is not used, these said dispersions and/or suspensions arecharacterised:

-   -   a) in that they have a OH⁻ ion concentration higher than or        equal to 1×10⁻² mole/l, and preferentially higher than or equal        to 2×10² mole/l,    -   b) in that they have a microbe concentration lower than or equal        to 100 microbes/gram, and preferentially less than or equal to        10 microbes/gram,    -   c) and in that they contain:        -   1. mineral matter,        -   2. water,        -   3. possibly at least one dispersing agent and/or at least            one grinding aid agent,        -   4. possibly at least one anti-foaming agent,        -   5. possibly at least one microbicidal agent.

According to this embodiment, these dispersions and/or suspensions arealso characterised in that they contain:

-   -   1. 0.1% to 85% by dry weight of mineral matter,    -   2. 15% to 99.9% by weight of water,    -   3. 0% to 5% by dry weight of at least one dispersing agent        and/or at least one grinding aid agent,    -   4. 0% to 5% by dry weight of at least one anti-foaming agent,    -   5. 0 to 5% by dry weight of at least one microbicidal agent,

relative to the total weight of the said dispersions and/or suspensions.

These aqueous dispersions and/or suspensions are also characterised inthat the substance with microbicidal effect is chosen from amongo-phenylphenol, it salts or again their mixtures, and/or at least oneproduct containing a germ which destroys microbial germs, preferablypseudomonas germs, and more preferably pseudomonas aeruginosa germs, andin that the destructive germ is from the Bdellovibrio family, and isvery preferentially the Bdellovibrio bacteriovorus germ.

Still according to this embodiment, and when, according to stage d) aprocess based on the increase of temperature is used, these aqueousdispersions and/or suspensions are also characterised in that themicrobial concentration is less than 10 microbes/gram.

In a second embodiment, in which stage c) of the process according tothe invention is used, and in which no substance with a microbicidaleffect is used according to stage d), these said aqueous dispersionsand/or suspensions are characterised:

-   -   a) in that they have a OH⁻ ion concentration lower than or equal        to 1×10⁻² mole/l, and preferentially lower than or equal to        1×10⁻³ mole/l, and very preferentially lower than or equal to        1×10⁻⁴ mole/l,    -   b) in that they have a microbe concentration lower than or equal        to 100 microbes/gram, and preferentially less than or equal to        10 microbes/gram,    -   c) and in that they contain:        -   1. mineral matter,        -   2. water,        -   3. at least one dispersing agent and/or at least one            grinding aid agent,        -   4. and possibly at least one anti-foaming agent,

According to this embodiment, these dispersions and/or suspensionsaccording to the invention are also characterised in that they contain:

-   -   1. 0.1% to 85% by dry weight of mineral matter,    -   2. 10% to 99.89% by weight of water,    -   3. 0.01% to 5% by dry weight of at least one dispersing agent        and/or at least one grinding aid agent,    -   4. 0% to 5% by dry weight of at least one anti-foaming agent,

relative to the total weight of the said dispersions and/or suspensions.

According to this embodiment, the anti-foaming agent is notably chosenfrom among siloxane compounds, fatty acid esters and their mixtures.

Still according to this embodiment, and when, according to stage d) aprocess based on the increase of temperature is used, these aqueousdispersions and/or suspensions are also characterised in that themicrobial concentration is less than or equal to 10 microbes/gram.

Another purpose of the invention consists in the use of the said aqueoussuspensions and/or dispersions of mineral matter in the mineralindustry, in the paper industry, preferably in the manufacture of paper,and/or in paper coating, and also in the field of manufacture ofwater-based paints, and also in lacquers and varnishes.

A final purpose of the invention lies in mineral formulations, paperformulations and notably paper sheets and coating colours, water-basedpaints, lacquers and varnishes characterised in that they contain thesaid suspensions and/or dispersions according to the invention.

The present invention is described in greater detail below usingexamples of embodiments and comparative examples. The invention is nothowever limited to the following examples. The skilled man in the art isable, without using any inventive activity, using the presentdescription, jointly with the claims, to formulate other examples and tofind other fields of application.

EXAMPLES

General Observations Concerning the Manner of Proceeding

The habitual methods for determining germs in the food products industryand in the paper and pigments industry are, for example, described inthe Swiss manual on food products, section 56, paragraph 7.01, edition1985, revision 1988, entitled “Bestimmung von aeroben Bakterien undKeime” and in the Swiss food products manual, section 56, paragraph7.22, edition 1985, revision 1988, entitled “Bestimmung von Pilzen”Habitually, the incubation time before being able to undertake thedetermination is each time approximately 48 hours. An incubation time of5 days is applied in order to detect the presence of spores.

The company Microbial Systems Ltd has developed the device and theprocess for analysing particles sold under the name Cellfacts™ R.Additional information on the subject is found in the journal entitledLabor flash 9/96, offering a reader service for the laboratory andresearch, Ott Verlag+ Druck AG, Ch-3607 Thun, Switzerland.

These devices enable the bacteria concentration in a sample to bedetermined, possibly by extrapolation, as particles present in anelectric field. The device in question together with the measurementmethod and the corresponding calculations are described in detail inEuropean patent EP 1 149 1 72.

The suspensions of pigments used in the examples were produced bygrinding and/or dispersion in the presence of sodium polyacrylates. Themass of the initial sample was 5 kg. A ball mill of the Dynomill type,of capacity equal to 2 litres, with a stirrer having a toothed disk ofdiameter 50 mm, was used. As a grinding body glass beads of diameter 2mm and zircon silicate beads of diameter 0.5 to 2 mm were used, but alsoother types of grinding balls such as, notably, porcelain, zirconiumsilicate, zirconium oxides such as baddeleyite, and their mixturesand/or aluminium oxides or autogenous grinding agents.

The aqueous suspensions and/or dispersions of mineral matter weresterilised for one hour at 141° C. in autoclaves for an examination ofthe protective effects of the process according to the invention.

The suspensions and/or dispersions were incubated for one week at 32° C.in an incubation oven, then mixed again with the corresponding quantityand type of tested is bacteria, for an examination of the curativeeffects of the process according to the invention.

At certain time intervals, the germs were quantified according to themethod “Bestimmung von aeroben mesophilen Keimen”, SchweizerischesLebensmittelbuch, section 56, paragraph 7.01, edition 1985, revision1988.

The OH⁻ ion molar concentration values were always determined at atemperature of 22° C. (the constant of dissociation of water, pKw, wasthen equal to 14)

$K = \frac{\left\lbrack {C_{H\; 3\; O}}^{+} \right\rbrack \times \left\lbrack C_{{OH}^{-}} \right\rbrack}{\left\lbrack C_{H\; 2\; O} \right\rbrack^{2}}$

For water at 22° C., in which C_(H30)+=C_(OH) ⁻ =10⁻⁷ M, we have:K_(water) (Kw) (22° C.)=10⁻¹⁴ M².

The constant of dissociation of water, pK_(w), is a function of thetemperature. Thus, a pH value 10 measured at 22° C. corresponds to a OH⁻ion concentration which would lead to a pH value equal to 11 if it weremeasured at 100° C.

Consequently, in order to take account of the influence of temperature,the following table was used to determine the values of the constant ofdissociation of water:

Temperature[° C.] K_(w) [M²] pK_(w) = −log₁₀ K_(w) 0 0.13 × 10⁻¹⁴ 14.8910 0.36 × 10⁻¹⁴ 14.45 16 0.63 × 10⁻¹⁴ 14.20 20 0.86 × 10⁻¹⁴ 14.07 221.00 × 10⁻¹⁴ 14.00 30 1.89 × 10⁻¹⁴ 13.73 50 5.60 × 10⁻¹⁴ 13.25 100 74.00× 10⁻¹⁴  12.13

Furthermore, in all the remainder of the present application, it isindicated that the expression Brookfield™ viscosity refers to theBrookfield™ viscosity measured on a viscometer of the same name and oftype RVT, at a speed of 100 RPM, using module no 3,

Example 1

The aim of this example is to illustrate the process according to theinvention, in its curative mode, applied to an aqueous suspension ofmineral matter which is calcium carbonate.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial germs to becontrolled in such a suspension, without modifying its stabilitysignificantly.

Pigment Suspension:

An aqueous suspension of 78.3% by weight of natural marble (of which 90%by weight of the particles have a diameter of less than 2 μm, and 65 byweight of the particles have a diameter of less than 1 μm), obtained bygrinding, was prepared, using 0.65% by dry weight of a polyacrylateneutralised by a commercially available sodium/magnesium mixture,relative to the dry weight of mineral matter.

The pH value of the suspension after grinding was 9.7 measured at 20° C.

Each time 2 samples of one kilogram of the pigment suspension wereprepared.

Microbial Suspension

A mixture of 7 different types of microbes was produced, gram-negatives,mainly produced from the family of pseudomonas (the majority beingpseudomonas aeruginosa), isolated from a suspension of calcium carbonatehaving germinated naturally, originating from Austria.

The 7 different varieties of microbes were able to be identified usingthe API™ test which is well known to the skilled man in the art, anddeveloped by the company BIOMERIEUX™.

In this suspension, the microbial germ concentration is 5×10⁶ germs/ml.

Sample 1

The 1^(st) sample corresponds to 1 kg of the said pigment suspension,which was mixed with 0.025 mole of OH⁻ ions through the addition ofsodium hydroxide, with substantial stirring. (NaOH was added as a 2.5molar solution).

The Brookfield™ viscosity immediately after the addition of sodiumhydroxide was 308 mPa·s.

Sample 2

The 2^(nd) sample was used as a comparative sample relative to the stateof the technique, and corresponds to 1 kg of the pigment suspensiondescribed at the start of example 1, without addition of the OH⁻ iondonator solution.

The Brookfield™ viscosity was 389 mPa·s.

Both samples were then mixed with 10 ml of microbial suspension and thenincubated each time for 24 hours at 30° C. in an incubation oven: in theremainder of the application, this action is designated under the termexposure. For each example, the samples are exposed to the samebacterial suspension.

For each sample the germ concentration (in number/ml), the OH⁻ ionconcentration values (in mole/l), and the Brookfield™ viscosity (mPa·s)were then measured.

This data is shown in tables 1 and 2.

TABLE 1 OH⁻ concentration Germ concentration (mole/l) (number/ml) Sample1 Sample 2 Sample 1 Sample 2 Immediately before the 1.6 × 10⁻² 5 × 10⁻⁵<10² <10² 1^(st) exposure Immediately after the 1.6 × 10⁻² 5 × 10⁻⁵ <10²1 × 10⁵ 1^(st) exposure Measure 3 days after 1.6 × 10⁻² 5 × 10⁻⁵ <10² 1× 10⁵ the 1^(st) exposure, then 2^(nd) exposure 4 days after the 2^(nd)1.6 × 10⁻² 5 × 10⁻⁵ <10² 4 × 10⁷ exposure

These results demonstrate the protective effect of the treatmentaccording to the invention on sample 1: there was no increase in thenumber of microbes.

TABLE 2 OH⁻ concentration Brookfield ™ viscosity (mole/l) (mPa · s)Sample 1 Sample 2 Sample 1 Sample 2 Immediately before 1.6 × 10⁻² 5 ×10⁻⁵ 310 390 the 1^(st) exposure 1 day after the 1^(st) 1.6 × 10⁻² 5 ×10⁻⁵ 518 463 exposure 5 days after the 1^(st) 1.6 × 10⁻² 5 × 10⁻⁵ 804676 exposure: 2^(nd) exposure 4 days after the 2^(nd) 1.6 × 10⁻² 5 ×10⁻⁵ 661 560 exposure 26 days after the 1^(st) 1.6 × 10⁻² 5 × 10⁻⁵ 907790 exposure: 26 days after the 1^(st) 1.6 × 10⁻² 5 × 10⁻⁵ 339 430exposure and after 5 minutes of intense stirring

In addition, the Brookfield™ viscosity of the sample according to theinvention is not modified: it changes in a manner similar to that of theuntreated sample.

Finally, the Brookfield™ viscosities at 26 days, measured afterstifling, are very close to the initial Brookfield™ viscosities: thetreatment according to the invention does not therefore modify thestability of the aqueous suspensions of mineral matter in terms of theBrookfield™ viscosity.

After 26 days, a part of sample 1 according to the invention having beensubject to the previous exposures was treated through the introductionof gaseous CO₂, so as to reduce the OH⁻ ion concentration to a valueequal to 5×10⁻⁵ mole/l.

This instant corresponds to the instant T=0 for this new sample.

This part of sample 1, henceforth called sample 1-2, and representingthe invention, will be subjected to a certain number of additionalexposures.

For sample 1-2 measurements of the OH⁻ ion concentration, of the numberof microbial germs, and of the Brookfield™ viscosity will then be taken.

The results are shown in tables 3 and 4.

TABLE 3 (sample 1-2) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 5 × 10⁻⁵ <10²Immediately after the 1^(st) exposure 6 × 10⁻⁵ 2 × 10⁶

TABLE 4 (sample 1-2) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) Immediately before the 1^(st) exposure 5 × 10⁻⁵ 238 1 dayafter the 1^(st) exposure 6 × 10⁻⁵ 580 5 days after the 1^(st) exposure:1 × 10⁻⁴ 790 2^(nd) exposure 12 days after the 1^(st) exposure 8 × 10⁻⁵648 26 days after the 1^(st) exposure 8 × 10⁻⁵ 998 26 days after the1^(st) exposure and 1 × 10⁻⁵ 358 after 5 minutes of intense stirring

The Brookfield™ viscosity without stirring of sample 1-2 according tothe invention only increases slightly over the duration of the storagerelative to the comparative sample. The stability is not degraded. TheBrookfield™ viscosity in the stirred state after 26 days is almostidentical to the initial Brookfield™ viscosity before the treatmentaccording to the invention: the stability of the sample according to theinvention is not thus modified in terms of the Brookfield™ viscosity.

After 26 days, another part of sample 1 according to the inventionhaving been subjected to the previous exposures as described at thestart of this example was treated through the introduction of nitricacid, so as to reduce the OH⁻ ion concentration to a value equal to8×10⁻⁵ mole/l.

This instant corresponds to the instant T=0 for this new sample.

This part of sample 1, henceforth called sample 1-3, and representingthe invention, will be subjected to a new exposure.

For sample 1-3 the measurements of the OH⁻ ion concentration and of thenumber of microbial germs will then be taken.

The results are shown in table 5.

TABLE 5 (sample 1-3) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 8 × 10⁻⁵ <10²Immediately after the 1^(st) exposure 1 × 10⁻⁴ 2 × 10⁵

The inhibitory effect was again eliminated through the addition of H₃O⁺ions by means of the addition of citric acid, i.e. by means of theprocess according to the invention.

After 26 days, another part of sample 1 according to the inventionhaving been subjected to the previous exposures as described at thestart of this example was treated through the introduction of phosphoricacid, so as to reduce the OH⁻ ion concentration to a value equal to2.5×10⁻⁵ mole/l.

This instant corresponds to the instant T=0 for this new sample.

This part of sample 1, henceforth called sample 1-4, and representingthe invention, will be subjected to a new exposure.

For sample 1-4 the measurements of the OH⁻ ion concentration and of thenumber of microbial germs will then be taken.

The results are shown in table 6,

TABLE 6 (sample 1-4) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 2.5 × 10⁻⁵ <10²Exposure 2.5 × 10⁻⁵ >10⁶

The inhibitory effect was again eliminated through the addition of H₃O⁺ions through the addition of citric acid, i.e. by means of the processaccording to the invention.

Example 2

The aim of this example is to illustrate the process according to theinvention, in its curative and protective mode, applied to an aqueoussuspension of mineral matter which is calcium carbonate.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial germs to becontrolled in such a suspension, without modifying its stability interms of Brookfield™ viscosity.

Pigment Suspension

An aqueous suspension of 78.3% by weight of natural marble (of which 90%by weight of the particles have a diameter of less than 2 μm, and 65% byweight of the particles have a diameter of less than 1 μm), obtained bygrinding, was prepared, using 0.65% by dry weight relative to the dryweight of mineral matter, of a polyacrylate neutralised by acommercially available sodium/magnesium mixture. The pH value of thesuspension after grinding was 9.7 measured at 20° C.

2 samples of 1 kg were prepared from the pigment suspension.

Microbial Suspension

A mixture of 7 types of different gram-negative bacteria was prepared,mostly comprised according to the family of pseudomonads (for the mostpart pseudomonas aeruginosa), isolated from a calcium carbonate slurryseeded naturally with germs, originating from Austria.

The 7 different varieties of microbes were able to be identified usingthe API™ test which is well known to the skilled man in the art, anddeveloped by the company BIOMERIEUX™.

The microbial germ concentration of this suspension is 5×10⁶ germs/ml.

Sample 3

This sample is used to illustrate the treatment according to theinvention, in its protective mode.

This sample corresponds to 1 kg of the said pigment suspension, whichwas mixed under substantial stirring, in a solution of ground Ca(OH)₂(with the average diameter of the particles being equal to 2 μm)containing 2.6×10⁻² mole/l of OH⁻ ions.

The Brookfield™ viscosity immediately after the previous addition was357 mPa·s.

This sample according to the invention was then mixed several times with10 ml of microbial suspension, and then incubated in an incubation oven,for 24 hours at 30° C.

Sample 3 was subjected to a number of exposures, and the OH⁻ ionconcentration, germ concentration (number/gram) and Brookfield™viscosity (mPa·s) values were then also measured.

The corresponding results are shown in tables 7 and 8.

TABLE 7 (sample 3) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 2 × 10⁻² <10²Immediately after the 1^(st) exposure 2 × 10⁻² <10² 3 days after the1^(st) exposure: 2 × 10⁻² <10² 2^(nd) exposure 4 days after the 2^(nd)exposure 2 × 10⁻² <10²

These results demonstrate the protective effect of the treatmentaccording to the invention on sample 3: there was no increase in thenumber of microbial germs.

TABLE 8 (sample 3) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) Immediately before the 1^(st) exposure 2 × 10⁻² 357 1 dayafter the 1^(st) exposure 2 × 10⁻² 909 5 days after the 1^(st) exposure:2 × 10⁻² 888 2^(nd) exposure 4 days after the 2^(nd) exposure 2 × 10⁻²747 26 days after the 1^(st) exposure 2 × 10⁻² 999 26 days after the1^(st) exposure and 2 × 10⁻² 420 after 5 minutes of intense stirring

In addition, the Brookfield™ viscosity of the sample according to theinvention is not modified: it changes in a manner similar to that of theuntreated sample, represented by sample 2.

Finally, the Brookfield™ viscosities at 26 days, measured afterstirring, are very close to the initial Brookfield™ viscosities: thetreatment according to the invention thus enables the Brookfield™viscosity to be regained.

After 26 days, a part of sample 3 according to the invention having beensubject to the previous exposures was treated through the introductionof gaseous CO₂, so as to reduce the OH⁻ ion concentration to a valueequal to 5×10⁻⁵ mole/l.

This instant corresponds to the instant T=0 for this new sample.

This part of sample 3, henceforth called sample 3-2, and representingthe invention, will be subjected to a certain number of exposures.

For sample 3-2, measurements of the OH⁻ ion concentration (mol/l), ofthe number of microbial germs (number/gram), and of the Brookfield™viscosity (mPa·s) will then be taken.

The corresponding results are shown in tables 9 and 10.

TABLE 9 (sample 3-2) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 5 × 10⁻⁵ <10²Immediately after the 1^(st) exposure 6 × 10⁻⁵ 2 × 10⁶

These results demonstrate that after reduction of the OH⁻ ionconcentration according to the invention, growth of microbial germs isrestarted: the process according to the invention thus enables thegrowth of microbial germs in aqueous suspension of mineral matter to becontrolled.

TABLE 10 (sample 3-2) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) Immediately before the 1^(st) exposure 5 × 10⁻⁵ 212 1 dayafter the 1^(st) exposure 5 × 10⁻⁵ 351 5 days after the 1^(st) exposure:6 × 10⁻⁵ 474 2^(nd) exposure 12 days after the 1^(st) exposure 8 × 10⁻⁵332 26 days after the 1^(st) exposure 8 × 10⁻⁵ 622 26 days after the1^(st) exposure and 6 × 10⁻⁵ 229 after 5 minutes of intense stirring

In addition, the Brookfield™ viscosity of the sample according to theinvention is not modified: it changes in a manner similar to that of theuntreated sample, represented by sample 2.

Finally, the Brookfield™ viscosities at 26 days, measured afterstirring, are very close to the initial Brookfield™ viscosities: thetreatment according to the invention thus enables the Brookfield™viscosity to be regained.

Sample 4

This sample is used to illustrate treatment according to the invention,in its curative mode.

This sample according to the invention corresponds to 1 kg of thepigment suspension described at the start of this example, and which wasmixed under substantial stirring with 10 ml of microbial suspension, andthen incubated in an incubation oven, for 7 days at 32° C. The microbialconcentration after one week's incubation was 2×10⁷ germs/ml.

This sample was mixed under substantial stirring, in a solution ofground Ca(OH)₂ (with the average diameter of the particles being equalto 2 μm) containing 2.6×10⁻² mole/l of OH⁻ ions.

The Brookfield™ viscosity immediately after the previous addition was389 mPa·s.

Sample 4 was subjected to a new exposure, and the OH⁻ ion concentration(mol/l), germ concentration (number/gram) and Brookfield™ viscosity(mPa·s) values were then also measured.

These results are shown in tables 11 and 12.

TABLE 11 (sample 4) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 2 × 10⁻² <10² 2 days after exposure 2 ×10⁻² <10² 7 days after exposure 2 × 10⁻² <10²

These results demonstrate the curative effect of the treatment accordingto the invention.

TABLE 12 (sample 4) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) 1 day after exposure 2 × 10⁻² 320 2 days after exposure 2 ×10⁻² 410 7 days after exposure 2 × 10⁻² 440

In addition, the Brookfield™ viscosities are not degraded.

After 7 days, a part of sample 4 according to the invention having beensubject to the previous exposures was treated through the introductionof gaseous CO₂, so as to reduce the OH⁻ ion concentration to a valueequal to 3×10⁻⁵ mole/l. This part of sample 4, named 4-2, was thenre-exposed to 1 ml of microbial suspension.

This instant corresponds to the instant T=0 for this new sample.

For sample 4-2, measurements of the OH⁻ ion concentration (mol/l), ofthe microbial germs concentration (number/gram), and of the Brookfield™viscosity (mPa·s) were then taken.

These results are shown in tables 13 and 14.

TABLE 13 (sample 4-2) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 4 × 10⁻⁵ <10² 2 days after exposure 4 ×10⁻⁵ <10² 7 days after exposure 3 × 10⁻⁵ 2 × 10⁶

These results demonstrate that the process according to the inventionenabled the microbial germ concentration to be increased anew: theprocess according to the invention thus enables the microbialconcentration in the sample to be controlled.

TABLE 14 (sample 4-2) OH⁻ Brookfield concentration viscosity (mole/l)(mPa · s) 1 day after exposure 4 × 10⁻⁵ 360 2 days after exposure 4 ×10⁻⁵ 330 7 days after exposure 3 × 10⁻⁵ 470

In addition, the Brookfield™ viscosities are not degraded by using theprocess according to the invention.

A part of sample 4, named sample 4-3, and resulting from the firstcurative preservation, was reduced to an OH⁻ ion concentration valueequal to 3×10⁻⁵ mole/l through the addition of liquid CO₂.

This sample was mixed under substantial stirring, in a solution ofground Ca(OH)₂ (with the average diameter of the particles being equalto 2 μm) containing 2.6×10⁻² mole/l of OH⁻ ions.

This moment was chosen as the new time origin.

The Brookfield™ viscosity immediately after the previous addition wasnow 425 mPa·s. The value of the OH⁻ ion concentration measured at 20° C.was 6.3×10⁻³ mole/l.

For sample 4-3, measurements of the OH⁻ ion concentration (mol/l), ofthe microbial germs concentration (number/gram), and of the Brookfield™viscosity (mPa·s) were then determined.

These results are shown in tables 15 and 16.

TABLE 15 (sample 4-3) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 6.3 × 10⁻³ <10² 2 days after exposure6.3 × 10⁻³ <10² 7 days after exposure 6.3 × 10⁻³ <10²

TABLE 16 (sample 4-3) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) 1 day after exposure 6.3 × 10⁻³ 410 2 days after exposure 6.3× 10⁻³ 440

These results demonstrate that the process according to the inventionenabled microbial growth to be stopped by a new increase in the OH⁻ ionconcentration: the process according to the invention thus enables themicrobial contamination in the sample to be controlled.

In addition, the Brookfield™ viscosities are not degraded.

After 7 days, a part of sample 4-3 according to the invention wastreated through the introduction of gaseous CO₂, so as to reduce the OH⁻ion concentration to a value equal to 3×10⁻⁵ mole/l. This part of sample4, named 4-4, was then re-exposed to 1 ml of microbial suspension.

This instant corresponds to the instant T=0 for this new sample.

For sample 4-4, measurements of the OH⁻ ion concentration (mol/l), ofthe microbial germs concentration (number/gram), and of the Brookfield™viscosity (mPa·s) were then taken.

TABLE 17 (sample 4-4) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 2.5 × 10⁻⁵ <10² 2 days after exposure2.5 × 10⁻⁵ 2 × 10⁶

These results demonstrate that the process according to the inventionenabled the microbial germ concentration to be increased anew: theprocess according to the invention thus enables the microbialconcentration in the sample to be controlled.

TABLE 18 (sample 4-4) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) 1 day after exposure 2.5 × 10⁻⁵ 560 2 days after exposure 2.5× 10⁻⁵ 530 7 days after exposure 2.5 × 10⁻⁵ 570

In addition, the Brookfield™ viscosities are not degraded by using theprocess according to the invention.

Example 3

The aim of this example is to illustrate the process according to theinvention, in its curative mode, applied to an aqueous suspension ofmineral matter which is kaolin.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial germs to becontrolled in such a suspension.

Pigment Suspension

An aqueous suspension was manufactured containing 63.3% by dry weight ofAmerican kaolin (Georgia) (of which 95% by weight of the particles havea diameter of less than 2 μm, and 70% by weight of the particles have adiameter of less than 1 μm), by grinding to a concentration of 25% byweight, followed by drying in a pulverisation drying machine, anddispersion in water with use of 0.25% by dry weight relative to the dryweight of mineral matter of commercially available sodium polyacrylate.

The pH value of the suspension after grinding was 7.7 measured at 20° C.

2 samples of 1 kg were prepared from the pigment suspension.

Microbial Suspension

A mixture of 7 different types of bacteria was produced, which weregram-negatives, mainly formed from the family of pseudomonads themajority being Pseudomonas aeruginosa), isolated from a suspension ofcalcium carbonate having germinated naturally, originating from Austria.

The 7 different varieties of microbes were able to be identified usingthe API™ test which is well known to the skilled man in the art, anddeveloped by the company BIOMERIEUX™.

The microbe concentration is 5×10⁶ germs/ml.

Sample 5

Sample 5 corresponding to 1 kg of the said pigment suspension was mixedunder substantial stilling in 0.053 mole of OH⁻ ions (added in the formof a CaO solution in ethylene glycol at a concentration of 2.7 M).

The Brookfield™ viscosity of the aqueous suspension of kaolinimmediately after addition of the CaO was 327 mPa·s.

The value of the OH⁻ ion concentration was 1.25×10⁻² mole/l.

Sample 6

Sample 6 illustrates the prior art and corresponds to the mixture of thepigment suspension and the microbial suspension.

By using the previous notations, samples 6 and 7 were subjected to anumber of exposures, and the OH⁻ ion concentration (mold), microbialgerm concentration (number/gram) and Brookfield™ viscosity (mPa·s)values were then measured.

These results are shown in tables 19 and 20.

TABLE 19 (samples 5 and 6) OH⁻ concentration Germ concentration (mole/l)(number/ml) Sample 5 Sample 6 Sample 5 Sample 6 Immediately before the1.25 × 10⁻² 5 × 10⁻⁷ <10² <10² 1^(st) exposure 1^(st) exposure 1.25 ×10⁻² 5 × 10⁻⁷ <10² 4 × 10⁵ 3 days after the 1^(st) 1.25 × 10⁻² 5 × 10⁻⁷<10² 9 × 10⁶ exposure: 2^(nd) exposure 4 days after the 2^(nd) 1.25 ×10⁻² 5 × 10⁻⁷ <10² 6 × 10⁷ exposure

These results illustrate the efficacy of the process according to theinvention in its protective aspect.

TABLE 20 (samples 5 and 6) OH⁻ concentration Brookfield ™ viscosity(mole/l) (mPa · s) Sample 5 Sample 6 Sample 5 Sample 6 Immediatelybefore 1.25 × 10⁻² 5 × 10⁻⁷ 444 394 the 1^(st) exposure 1 day after the1^(st) 1.25 × 10⁻² 5 × 10⁻⁷ 518 463 exposure 5 days after the 1^(st)1.25 × 10⁻² 5 × 10⁻⁷ 804 676 exposure: 2^(nd) exposure 4 days after the2^(nd) 1.25 × 10⁻² 5 × 10⁻⁷ 1150 855 exposure 26 days after the 1^(st)1.25 × 10⁻² 5 × 10⁻⁷ 1907 1190 exposure 26 days after the 1^(st) 1.25 ×10⁻² 5 × 10⁻⁷ 565 444 exposure and after 5 minutes of intense stirring

Moreover, the Brookfield™ viscosities of the sample according to theinvention are not degraded relative to the sample representing the priorart.

After 26 days, a part of sample 5 according to the invention having beensubject to the previous exposures was treated through the introductionof gaseous CO₂, so as to reduce the OH⁻ ion concentration to a valueequal to 2×10⁻⁶ mole/l.

This instant corresponds to the instant T=0 for this new sample.

This part of sample 5, henceforth called sample 5-2, and representingthe invention, will be subjected to a certain number of exposures.

For sample 5-2, measurements of the OH⁻ ion concentration (mol/l), ofthe number of microbial germs (number/grain), and of the Brookfield™viscosity (mPa·s) will then be taken.

These results are shown in tables 21 and 22.

TABLE 21 (sample 5-2) OH⁻ Germ concentration concentration (mole/l)(number/ml) Immediately before the 1^(st) exposure 2 × 10⁻⁶ <10²Exposure 4 × 10⁻⁶ 2 × 10⁶

These results demonstrate that the process according to the inventionenabled the microbial germ concentration to be increased anew: theprocess according to the invention thus enables microbial growth in theaqueous suspension of mineral matter to be controlled.

TABLE 22 (sample 5-2) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) Immediately before the 1^(st) exposure 2 × 10⁻⁶ 638 1 dayafter the 1^(st) exposure 2 × 10⁻⁶ 680 5 days after the 1^(st) exposure:3 × 10⁻⁶ 790 2^(nd) exposure 12 days after the 1^(st) exposure 4 × 10⁻⁶948 26 days after the 2^(nd) exposure 8 × 10⁻⁶ 1198 26 days after the1^(st) exposure and 6 × 10⁻⁶ 688 after 5 minutes of intense stirring

Moreover, the Brookfield™ viscosities are not degraded relative to thesample representing the prior art.

Example 4

The aim of this example is to illustrate the process according to theinvention, in its curative and protective modes, applied to an aqueoussuspension of mineral matter which is kaolin, and in the event that theprocess according to the invention uses a biocide according to stage d)which is o-phenylphenol.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial germs to becontrolled in such a suspension.

Pigment Suspension

An aqueous suspension containing 78.3% by dry weight of natural calciumcarbonate which is marble (of which 90% by weight of the particles havea diameter of less than 2 μm, and 65% by weight of the particles have adiameter of less than 1 μm), obtained by grinding, was prepared, using0.65% by dry weight relative to the dry weight of mineral matter, of acommercially available polyacrylate neutralised by a sodium/magnesiummixture.

The pH value of the suspension after grinding was 9.7, measured at 20°C.

2 samples of 1 kg were prepared from the pigment suspension.

Microbial Suspension

A mixture, formed from 7 types of different gram-negative bacteria, wasprepared, mostly comprised according to the family of pseudomonads (forthe most part Pseudomonas aeruginosa), isolated from calcium carbonatesuspensions having germinated naturally, originating from Austria.

The 7 different varieties of microbes were able to be identified usingthe API™ test which is well known to the skilled man in the art, anddeveloped by the company BIOMERIEUX™.

The microbe concentration is 5×10⁶ germs/ml.

Sample 7

This sample is used to illustrate the process according to the inventionin its curative mode, and in combination with a biocide which iso-phenylphenol.

This sample according to the invention corresponding to 1 kg of the saidpigment suspension was mixed under stirring in 10 ml of microbialsuspension and then incubated for 7 days at 32° C. in an incubationoven.

The bacterial concentration after one week's incubation was 2×10⁷germs/ml.

After this, 200 ppm of o-phenylphenol was added to the sample undersubstantial stirring, in the form of a 45% solution of o-phenylphenol,dissolved in a solution containing KOH at a concentration of 1.07 molesKOH per mole of o-phenylphenol. 1270 ppm of Ca(OH)₂ was also added as afinely ground suspension (the average diameter of the particles aftergrinding was 2 at a concentration of 2.7 molar Ca(OH)₂.

The Brookfield™ viscosity of the suspension of calcium carbonateimmediately after addition of the CaO was 271 mPa·s.

This sample according to the invention was then mixed several times with10 ml of microbial suspension, and then incubated each time in anincubation oven, for 24 hours at 30° C.

The OH⁻ ion concentration (mol/l), microbial germs concentration(number/gram), and Brookfield™ viscosity (mPa·s) values were thendetermined.

These results are shown in tables 23 and 24.

TABLE 23 (sample 7) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 1.58 × 10⁻² <10² 2 days after exposure1.58 × 10⁻² <10² 7 days after exposure 1.58 × 10⁻² <10²

These results demonstrate that the process according to the inventionenables a curative treatment of the aqueous suspension of mineral matterto be obtained.

TABLE 24 (sample 7) OH⁻ Brookfield ™ concentration viscosity (mole/l)(mPa · s) Immediately before exposure 1.58 × 10⁻² 271 1 day afterexposure 1.58 × 10⁻² 698 4 days after exposure 1.58 × 10⁻² 823 25 daysafter exposure 1.58 × 10⁻² 872 25 days after exposure and after 1.58 ×10⁻² 282 5 minutes of intense stirring

Moreover, the Brookfield™ viscosities of the aqueous suspension ofmineral matter according to the invention are not degraded.

Sample 8

This sample is used to illustrate the prior art and uses a biocide whichis o-phenylphenol.

The second sample according to the invention corresponding to 1 kg ofthe said pigment suspension was mixed under substantial stirring with 10ml of microbial suspension and then incubated in an incubation oven for7 days at 32° C.

The microbial concentration after one weeks incubation was 2×10germs/ml.

200 ppm of o-phenylphenol was then added to this second sample undersubstantial stirring, in the form of a 45% solution of o-phenylphenol,dissolved by 1.07 mole of KOH per mole of o-phenylphenol.

The Brookfield™ viscosity immediately after the addition ofo-phenylphenol was 285 mPa·s.

The OH⁻ ion concentration (mol/l) and microbial germs concentration(number/gram) values were then determined.

These results are shown in table 27.

TABLE 27 (sample 8) OH⁻ Germ concentration concentration (mole/l)(number/ml) 1 day after exposure 6.3 × 10⁻⁵ >10² 2 days after exposure6.3 × 10⁻⁵ >10⁴ 7 days after exposure 6.3 × 10⁻⁵ >10⁵

Sample 8, representing the prior art, shows that the o-phenylphenolpresents an insufficient microbicidal effect, in relation to the germsused in the curative range.

Preservation is incomplete and is not sufficient. Conversely, withsample 7 according to the invention, it was possible to show that theprocess according to the invention which combines the use ofo-phenylphenol and a stage of increase of the OH⁻ ion concentrationenables very satisfactory results to be obtained in respect of thereduction of microbial germs in the aqueous suspension of mineralmatter.

Example 5

The aim of this example is to illustrate the process according to theinvention in its curative and protective modes in relation to wagonwashing water.

Preservation of Wagon Washing Water

in order to simulate wagon washing water, a buffered kitchen saltsolution was used, comprising 3% by weight of a suspension of calciumcarbonate, taken from example 1.

The disinfection test was then undertaken on two different samples.

Sample 9

This sample is used to illustrate the process according to the inventionin its protective mode.

The Ca(OH) was dissolved in a buffered solution of sterile phosphate at0.85% by weight (PBS) and was mixed after 24 hours' storage at 30° C.with the bacteria/yeasts cocktail indicated in table 28.

The samples were incubated once more for 24 hours at 30° C. and thenremoved from the plates.

The germs which had grown were examined under an optical microscope.

Sample 10

This sample is used to illustrate the process according to the inventionin its curative mode.

A cocktail of bacteria (in PBS), firstly, and a bacteria/yeasts cocktailin (PBS), secondly, were mixed with Ca(OH)₂, stored, and then removedfrom their moulds.

TABLE 28 (Composition of microbe cocktail) Type of bacteria ObservationsBacteria cocktail without yeast: Pseudomonas aeruginosa Gram-negative,not Enterobacteriacae Pseudomonas Pseudoalcaligenes Gram-negative, notEnterobacteriacae Pseudomonas stuzeri Gram-negative, notEnterobacteriacae Acinetobacter baumannii/calco Gram-negative,enterobacteriacae Klebsiella spp. Gram-negative, enterobacteriacaeBazillus subtilis Gram-positive, former of spores Bazillus spp.Gram-positive, Staphylococcus cohnii cohnii Gram-positive, Koc.Varians/rosea Gram-positive, Micrococcus kristae Gram-positive, “Yeasts”and others: Candida albicans, eucaryote, Yeast monocellular with stronggrowth Rosa Germ isolated from a solution of sodium not specified inpolyacrylate, resistant to formaldehyde greater detail Rosarot Germisolated from a paper machine not specified in circuit, a germ with anunstable gram value detail

Tables 29 and 30 indicate the OH⁻ ion concentration (mole/l) and theyeast germ concentration (number/ml) measured in the samples, after24-hours' incubation, for different initial concentrations of Ca(OH)₂.

TABLE 29 (sample 9) 0 200 500 1000 2000 ppm ppm ¹⁾ ppm ¹⁾ ppm ¹⁾ ppm ¹⁾microbial 10³ 10³ 30 <10 <10 germs con- centration (number/ml) OH⁻ 3 ×10⁻⁷ 5 × 10⁻⁴ 3 × 10⁻³ 1 × 10⁻² 5 × 10⁻² ion con- centration (mole/l) ¹⁾Dosage of Ca(OH)₂: Active quantity/Global

TABLE 30 (sample 10) 0 ppm 200 ppm ¹⁾ 500 ppm ¹⁾ 1000 ppm ¹⁾ microbialgerms 10⁵ 10⁵ 30 <10 (number/ml) OH⁻ ion 3 × 10⁻⁷ 4 × 10⁻⁵ 3 × 10⁻³ 1 ×10⁻² concentration (mole/l) ¹⁾ Dosage of Ca(OH)₂: Active quantity/Global

Thus, table 29 demonstrates that for an initial Ca(OH)₂ concentration of200 ppm, after 24-hour a microbial germ concentration of 1000/ml isobtained, and an OH⁻ ion concentration of 5×10⁻⁴ mole/1.

The value of the microbial germ concentration was reduced to 50/ml, foran initial Ca(OH)₂ concentration of 500 ppm; an OH⁻ ion concentration of3×10⁻³ mole/l is then obtained.

These results indeed demonstrate the protective effect of the processaccording to the invention.

Finally, the value of the microbial germ concentration is reduced to aquantity less than 10/ml, for an initial Ca(OH)₂ concentration of 500ppm; an OH⁻ ion concentration of 3×10⁻³ mole/l is then obtained.

This latter result illustrates the fact that with the process accordingto the invention used in its protective mode it is possible to obtainaqueous suspensions of mineral matter with a very low quantity ofmicrobial germs, notably a quantity of less than 10 per ml.

At the same time, table 30 demonstrates the efficacy of the processaccording to the invention in its curative mode since, after 24 hours,the microbe concentration is reduced particularly if the initial Ca(OH)₂concentration is substantial.

It is thus noted that with an initial Ca(OH)₂ concentration of 1000 ppm,a very large part of the microbial germs is destroyed since theirconcentration is less than 10 per ml after 24 hours.

This latter result illustrates the fact that with the process accordingto the invention used in its curative mode it is possible to obtainaqueous suspensions of mineral matter with a very low quantity ofmicrobial germs, notably a quantity of less than 10 per ml.

Samples 9 and 10 of initial Ca(OH)₂ concentration equal to 1000 ppm werethen removed from their mould at 30° C. on to a bacterial medium calleda PCA (Plate Count Agar).

It is indicated that these media correspond to a bacterial formulationdescribed in the following works: “American Public Health Association:Standard Methods for the Examination of Dairy Products, 15th ed., 1985”,“American Public Health Association, American Water Works Associationand Water Pollution Control Federation: Standard Methods for theExamination of Water and Wastewater, 20th ed., Washington, 1998” and “Animproved agar medium for the detection of proteolytic organisms in totalbacterial counts, J. Appl, Bact., 33; 363-370 (1970)”.

After 48 hours' incubation, the samples are once again removed fromtheir moulds on to the same medium of type PCA.

In terms of microbial germs, fewer than 40 bacteria per ml are counted,and fewer than 100 microbes other than bacteria per ml.

These results thus illustrate the efficacy of the process according tothe invention in its curative mode.

For a part of sample 9, named 9-2, the OH⁻ ion concentration was reducedto a value of 5×10⁻⁷ mole/l by the addition of gaseous CO₂. It wasincubated once again for 24 hours in the presence of the cocktail ofbacteria and yeasts described in table 28. It was then removed from itsmould on to a bacterial medium of type PCA, as described previously.

As previously, the microbial germ concentration as a function of theinitial Ca(OH)₂ concentration was then measured: these results are shownin table 31.

TABLE 31 (sample 9-2) 0 ppm 200 ppm ¹⁾ 1000 ppm ¹⁾ microbial germconcentration >10⁴ >10⁵ >10⁵ (number/ml) OH⁻ ion concentration (mole/l)1 × 10⁻⁶ 1 × 10⁻⁶ 1 × 10⁻⁶ ¹⁾ Dosage of Ca(OH)₂: Active quantity/Global

These results demonstrate that by reducing the OH⁻ ion concentrationthrough the addition of liquid CO₂ it was possible, using the processaccording to the invention, to cancel the protective effect and restartmicrobial growth.

Example 6

This example illustrates the process according to the invention in whichthe stage of reduction of the OH⁻ ion concentration is combined with aphysical process, which in this case is a process based on increasingthe temperature.

Pigment Suspension

An aqueous suspension containing OA % by dry weight of natural calciumcarbonate which is marble (of which 90% by weight of the particles havea diameter of less than 2 μm, and 65% by weight of the particles have adiameter of less than 1 μm), obtained by grinding, was prepared, using0.65% by dry weight relative to the dry weight of mineral matter, of acommercially available polyacrylate neutralised by a sodium/magnesiummixture.

2 samples were prepared each time.

Microbe Suspension

A microbe suspension of concentration equal to 10⁴ microbes/g, thecomposition of which is given by table 32, was prepared.

Sample 11

This sample illustrates the invention and consists of a pigmentsuspension, in which the microbe suspension was mixed, and into which asolution containing 500 ppm of Ca(OH)₂ was introduced.

This sample was incubated for 24 hours at 20° C.

Sample 12

This sample illustrates the prior art and is identical to sample 11,except that it does not contain Ca(OH)₂.

This sample was incubated fix 24 hours at 20° C.

Sample 13

This sample illustrates the invention and consists of a pigmentsuspension, in which the microbe suspension was mixed, and into which asolution containing 500 ppm of Ca(OH)₂ was introduced.

This sample was incubated for 24 hours at 40° C.

Sample 14

This sample illustrates the prior art and is identical to sample 13,except that it does not contain Ca(OH)₂.

This sample was incubated for 24 hours at 40° C.

TABLE 32 (composition of microbe cocktail) Type of bacteria ObservationsBacteria cocktail without yeast: Pseudomonas aeruginosa Gram-negative,not Enterobacteriacae Pseudomonas Pseudoalcaligenes Gram-negative, notEnterobacteriacae Pseudomonas stuzeri Gram-negative, notEnterobacteriacae Acinetobacter baumannii/calco Gram-negative,enterobacteriacae Klebsiella spp. Gram-negative, enterobacteriacaeBazillus subtilis Gram-positive, former of spores Bazillus spp.Gram-positive, Staphylococcus cohnii Gram-positive, Koc. Varians/roseaGram-positive, Micrococcus kristae Gram-positive, “Yeasts” and others:Candida albicans, eucaryote, Yeast monocellular with high growth RosaGerm isolated from solution of sodium not specified in polyacrylate,resistant to formaldehyde greater detail Rosarot Germ isolated from apaper machine not specified in circuit, a germ with an unstable gramvalue detail

For each sample the OH⁻ ion concentration (mole/l) was measured,together with the bacteria concentration and the concentration inmicrobes other than bacteria (number/ml); these results are shown intable 33.

TABLE 33 Sample 12 Sample 14 Sample 11 Sample 13 Temperature 20° C. 40°C. 20° C. 40° C. Initial Ca(OH)₂ 0 500 0 500 concentration (ppm)Bacteria concentration >10⁴ >10⁴ 2 × 10⁴ <10 (number/ml) Concentrationin >10⁴ >10⁴ 2 × 10³ <10 microbes other than bacteria (number/ml) OH⁻ion 2 × 10⁻⁷ 2 × 10⁻⁷  3 × 10⁻³ 3 × 10⁻³ concentration (mole/l)

Table 33 demonstrates that the stage of reduction of the OH⁻ ionconcentration, which is representative of the process according to theinvention, allows, at 20° C., the number of microbial germs of all typesto be reduced (sample 11).

It also demonstrates that this stage of reduction of the OH⁻ ionconcentration, in combination with a physical process which is anincrease of the temperature to 40° C., the said combination also beingrepresentative of the process according to the invention, enables theconcentration in microbes of all types to be reduced in very markedfashion, since this concentration is then less than 10 per ml.

For samples 11 and 13 according to the invention, the OH⁻ ionconcentration was then reduced to a value of 3.2×10⁻⁶ mole/l through theaddition of CO₂. These samples were then once again incubated in themicrobial cocktail described above, and then removed from their mouldson to a microbial cocktail of type PCA at 30° C., and the said cocktailwas left to act for 24 hours.

The OH⁻ ion concentration is then equal to 1×10⁻⁴ mole/l and a newincrease of the microbial germs is then observed: by means of theprocess according to the invention, it was thus possible to restart themicrobial growth.

Example 7

The aim of this example is to illustrate the process according to theinvention, in its curative mode by grinding, applied to an aqueoussuspension of mineral matter which is calcium carbonate.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial germs to becontrolled in such a suspension, without modifying its stability interms of Brookfield™ viscosity.

Microbial Suspension

A mixture of 7 types of different gram-negative bacteria was prepared,mostly comprised according to the family of pseudomonads (for the mostpart pseudomonas aeruginosa), isolated from a calcium carbonate slurryseeded naturally with germs, originating from Austria.

The 7 different varieties of microbes were able to be identified usingthe API™ test which is well known to the skilled man in the art, anddeveloped by the company BIOMERIEUX™.

The microbe concentration is 5×10⁶ germs/ml.

Sample 15

This sample is used to illustrate the prior art; it is obtained byexposure of a suspension of calcium carbonate to the microbialsuspension, then by grinding of the said suspension of calciumcarbonate.

5 kg of dry calcium carbonate was prepared, from an aqueous suspensionof 77.3% by dry weight of natural marble (of which 30% by weight of theparticles have a diameter of less than 2 μm, and 8% by weight of theparticles have a diameter of less than 1 μm).

The said suspension was treated with 10 ml of the microbial suspensionand stored for 24 hours at 30° C.

By grinding with 0.65% by dry weight relative to the dry weight ofmineral matter of a polyacrylate neutralised by a commercially availablemixture of sodium and magnesium, a suspension was produced in which 88%by weight of the particles have a diameter of less than 2 μm, and 64% byweight of the particles have a diameter of less than 1 μm.

The pH value of the suspension after grinding was 9.7 measured at 20° C.

The Brookfield™ viscosity 24 hours after grinding was 284 mPa·s.

The microbial germ concentration of this suspension after grinding wasgreater than 10⁻⁵ germs/ml.

Sample 16

This sample is used to rate the treatment according to the invention, inits protective mode.

5 kg of dry calcium carbonate was prepared, from an aqueous suspensionof 77.1% by weight of natural marble (of which 30% by weight of theparticles have a diameter of less than 2 μm, and 8% by weight of theparticles have a diameter of less than 1 μm).

The said suspension was treated with 10 ml of the microbial suspensionand stored for 24 hours at 30° C.

After this, this sample was mixed under substantial stirring, in asolution of ground Ca(OH)₂ (with the average diameter of the particlesbeing equal to 2 μm) containing 2×10⁻² mole/l of OH⁻ ions.

By grinding with 0.65% by dry weight relative to the dry weight ofmineral matter of a polyacrylate neutralised by a commercially availablemixture of sodium and magnesium, a suspension was produced in which 91%by weight of the particles have a diameter of less than 2 μm, and 66% byweight of the particles have a diameter of less than 1 μm.

The value of the suspension after grinding was 12.2 measured at 20° C.

The Brookfield™ viscosity measured 24 hours after the previous additionwas 253 mPa·s.

The germ concentration of this suspension after grinding was less than10² germs/ml.

These results demonstrate that the process according to the inventionhas enabled the microbial contamination of the sample to be reduced veryclearly relative to the treatment of the prior art, without howevermodifying the stability of the sample according to the invention interms of Brookfield™ viscosity.

After 2 days, sample 16 according to the invention was treated throughthe introduction of gaseous CO₂, so as to reduce the OH⁻ ionconcentration to a value equal to 2×10⁻⁵ mole/1.

The Brookfield™ viscosity 24 hours after the previous addition of CO₂was 222 mPa·s.

The germ concentration of this suspension after grinding was less than10² germs/ml.

Subsequently, sample 16 according to the invention was again treated bythe introduction of gaseous CO₂.

It was then treated with 1 ml of microbial suspension and stored at 30°for 48 hours. The germ concentration of this suspension was then greaterthan 10⁶ germs/ml. These results demonstrate that the process accordingto the invention, through the addition of gaseous CO₂, enabled themicrobial growth to be stimulated in the sample.

Example 8

The aim of this example is to illustrate the process according to theinvention, in its curative mode, applied to an aqueous suspension ofmineral matter which is a precipitated calcium carbonate.

Its aim is also to illustrate that the process according to theinvention allows the development of the growth of microbial genus to becontrolled in such a suspension.

Pigment Suspension:

An aqueous suspension was manufactured containing 50.0% by dry weight ofcarbonate precipitate of the Syncarb™ F 474 type, sold by the companyOMYA™. The pH value of the suspension was 9.7 measured at 20° C.

2 samples of 1 kg were prepared from the pigment suspension.

Bacterial Suspension:

A mixture of 7 different types of bacteria was produced, which weregram-negatives, mainly formed from the family of pseudomonads (themajority being Pseudomonas aeruginosa), isolated from a suspension ofcalcium carbonate having germinated naturally, originating from Austria.

The germ concentration is 2×10⁵ germs/ml.

Sample 17

The first sample of 1 kg of suspension of precipitated calcium carbonatewas mixed under vigorous stirring with 0.075 mole of OH⁻ ions (added inthe form of a 2.7 molar suspension of Ca(OH)₂ in water).

The viscosity of the suspension of precipitated calcium carbonateimmediately after addition of the Ca(OH)₂ was equal to 227 mPa·s.

The pH of the suspension was equal to 12.1.

This suspension now corresponds to sample 17 which illustrates theinvention.

Sample 18

The other 1 kg sample of precipitated calcium carbonate suspension wasmixed with the bacterial suspension.

The viscosity of this suspension was equal to 257 mPa·s.

This suspension now corresponds to sample 18 which illustrates the priorart.

Samples 17 and 18 were then subjected to a number of exposures, asindicated in table 34. The OH⁻ ion concentration was determined for eachof them, together with the microbial germ concentration at differenttimes (according to the previously described methods), as also indicatedin table 34.

TABLE 34 Time Event OH⁻ concentration Germ concentration (T = (Exposure(mole/l) (number/ml) number and/or Sample Sample Sample Sample of days)measurements) 17 18 17 18 T = 0 Measurements 2 × 10⁻² 7.5 × 10⁻⁵  <10²3.3 10⁴ T = 2 Exposure and 2 × 10⁻² 1 × 10⁻⁴ <10²  >10⁵ measurements T =4 Exposure and 2 × 10⁻² 1 × 10⁻⁴ <10² >>10⁵ measurements

These results illustrate the efficacy of the process according to theinvention in its protective aspect.

In addition, the viscosities of sample no 17 according to the inventionmeasured at T=2 days and T=4 days are equal to 227 mPa·s and 232 mPa·s:they are thus not degraded compared to the sample representing the priorart.

After 4 days, a part of sample 17 according to the invention was treatedthrough the introduction of gaseous CO₂, so as to reduce the OH⁻ ionconcentration to a value of 4×10⁻⁶ mole/litre.

This part of sample 17 is henceforth called sample 17b.

This sample 17b was then subjected to a number of exposures, asindicated in table 35.

The OH⁻ ion concentration was then determined, together with themicrobial germ concentration at different times (according to thepreviously described methods), as indicated in table 35 (instant T=0corresponds to the time of introduction of gaseous CO₂ into sample 17,henceforth called sample 17b).

TABLE 35 Time (T = Event (exposure OH⁻ Germ number and/or concentrationconcentration of days) measurements) (mole/litre) (number/ml) T = 0Measurements 4 × 10⁻⁶ <10² T = 2 days Exposure 4 × 10⁻⁶ 2.7 10³Measurements T = 4 days Exposure 4 × 10⁻⁶ >10⁵ Measurements

These results demonstrate that the process according to the inventionenabled the germ concentration to be increased anew: the processaccording to the invention thus enables microbial growth in the aqueoussuspension of precipitated calcium carbonate to be controlled.

The invention claimed is:
 1. An aqueous suspension of mineral mattercomprising calcium carbonate, at least one dispersing agent, and anantimicrobial agent consisting of one or more OH⁻ ion donors selectedfrom alkali oxides and alkali hydroxides, wherein the aqueous suspensionis obtained by a process for disinfecting or preserving the aqueoussuspension of or from microbial contamination, wherein the processcomprises: a) at least one stage to increase and maintain the OH⁻ ionconcentration of the aqueous suspension of the mineral matter comprisingcalcium carbonate, to a value greater than or equal to 1×10⁻² mole/l, byaddition of the antimicrobial agent consisting of one or more OH⁻ iondonors selected from alkali oxides and alkali hydroxides, for asufficient time to disinfect or preserve the aqueous suspension of themineral matter comprising calcium carbonate of or from microbialcontamination, and b) at least one stage of dispersion and/or grindingof the aqueous suspension of the mineral matter comprising calciumcarbonate, occurring before, during or after stage a), wherein theaqueous suspension of mineral matter has a microbe concentration of lessthan or equal to 100 microbes/gram.
 2. The aqueous suspension accordingto claim 1, wherein the OH⁻ ion concentration value in stage a) ishigher than or equal to 2×10⁻² mole/l.
 3. The aqueous suspensionaccording to claim 1, wherein the one or more OH⁻ ion donors added instage a) is an alkali oxide.
 4. The aqueous suspension according toclaim 1, wherein the one or more OH⁻ ion donors added in stage a) is analkali hydroxide.
 5. The aqueous suspension according to claim 1,wherein the one or more OH⁻ ion donors added in stage a) is NaOH.
 6. Theaqueous suspension according to claim 1, wherein stage b) is conductedusing at least one dispersing agent or at least one grinding aid agent.7. The aqueous suspension according to claim 1, wherein a physicaldecontamination is introduced before, during or after stage a), and/orb).
 8. The aqueous suspension according to claim 7, wherein the physicaldecontamination uses at least one treatment process based on an increaseof temperature.
 9. The aqueous suspension according to claim 1, whereinthe mineral matter is natural and/or precipitated calcium carbonate. 10.The aqueous suspension according to claim 1, wherein the mineral matteris natural calcium carbonate.
 11. The aqueous suspension according toclaim 1, wherein the mineral matter is marble, calcite, chalk or theirmixtures.
 12. A paper formulation comprising or manufactured with thesuspension according to claim
 1. 13. A sheet of paper comprising ormanufactured with the suspension according to claim
 1. 14. A coatingcolor comprising or manufactured with the suspension according toclaim
 1. 15. A water-based paint comprising or manufactured with thesuspension according to claim
 1. 16. A lacquer comprising ormanufactured with the suspension according to claim
 1. 17. A varnishcomprising or manufactured with the suspension according to claim 1.